High dynamic range imaging is used in optical imaging and photography to reproduce a greater range of luminosity than is possible with imaging techniques using smaller luminance ranges for each image exposure. HDR (high dynamic range) can present a range of luminance in an image that is more similar to the capacity of the human eye. The human eve uses an iris to constantly adapt to a broad range of luminance in a viewed scene. The brain continuously interprets this viewed information so the viewer can see in a wide range of light conditions. In contrast, existing imaging technology generally captures smaller luminance ranges in a captured image.
HDR images can represent a greater range of luminance levels than can be achieved using devices which capture lower luminance ranges. Examples of scenes with a greater range of luminance that can be captured can include many real-world scenes containing very bright, direct sunlight to extreme shade, dark images with a larger luminance range or faint images of space. HDR images are often created by combining multiple, narrower range exposures of the same scene or subject. Most image sensors or cameras take photographs with a limited exposure range resulting in the loss of detail in highlights or shadows.
HDR images can be created from merging multiple low-dynamic-range (LDR) or standard-dynamic-range (SDR) photographs. HDR images can also be acquired using special image sensor configurations that are expensive, such as the use of multiple camera heads which can be used for capturing images with multiple exposure levels used in HDR images.